Common Cloud Names, Shapes, and Altitudes:

Common Cloud Names, Shapes, and Altitudes:

Low Clouds Middle Clouds High Clouds Genus Cumulus Cumulonimbus (extend through all 3 levels) Stratus Stratocumulus Altocumulus Altostratus Nimbostratus (extend through 1+ levels) Cirrus Cirrocumulus Cirrostratus Species (can be only one) humilis mediocris congestus fractus calvus capillatus nebulosus fractus stratiformis lenticularis castellanus stratiformus lenticularis castellanus floccus (none) (none) fibratus uncinus spissatus castellanus floccus stratiformis lenticularis castellanus floccus fibratus nebulosus Varieties (can be more than one) radiatus (none) opacus, translucidus, undulatus translucidus, perlucidus, opacus, duplicatus, undulatus, radiatus, lacunosus translucidus, perlucidus, opacus, duplicatus, undulatus, radiatus, lacunosus translucidus, perlucidus, opacus, duplicatus, undulatus, radiatus (none) intortus, radiatus, vertebratus, duplicatus undulatus, lacunosus duplicatus, undulatus Cloud Classification: Clouds are classified using a Latin Linnean system based on genera and species, originally developed by Luke Howard, an amateur meteorologist and Quaker in 1802. The modern classification scheme is based on Howard s system and is detailed in The International Cloud Atlas, published by the World Meteorological Organization since 1896. In addition to standardizing the genus-species system, the WMO also classified clouds by altitude and divided the troposphere into 3 levels: Low-level Clouds: < 6,500 ft. Mid-level Clouds: 6,500 to 23,000 ft. High-level Clouds: 16,500 to 45,000 ft.

Cumulus Clouds ( The cloud of choice for 6-yr.-olds ) Typical Altitude: 2,000-3,000 ft. Location: Worldwide (except in Antartica, where it s too cold) There are three species of cumulus clouds: humilis are wider than they are tall mediocris are as wide as they are tall congestus are taller than they are wide Precipitation: Generally none, except for brief showers from congestus Composition: Liquid water Formation: Thermal convection currents Often called fair-weather clouds, cumulus clouds are common over land on sunny days, when the sun heats the land creating thermal convection currents Each thermal is distinct, and, consequently, each cumulus cloud is a distinct puff

Cumulonimbus Clouds ( The towering thunderclouds that scare us senseless ) Three critical conditions for cumulonimbus formation: Ready supply of warm, moist air, which rises at speeds of up to 25-70 mph Tropospheric winds need to increase considerably with height to encourage it to slant forward Typical Altitude: 2,000-45,000 ft. Location: Common in tropics and temperate regions, rare at poles Precipitation: Heavy downpours, hail Composition: Liquid water throughout, ice crystals at the top Formation: Upwardly mobile cumulus congestus clouds (thermals) The atmosphere around the cloud needs to be unstable no temp. inversions here

Stratus Clouds ( The clouds that weigh heavily on your mood ) Stratus clouds are the lowest forming and are often called fog or mists when they are earth-bound Stratus clouds are formed when a large air mass cools at the same time (e.g. a warm air parcel drifts into or above a cooler region) Typical Altitude: 0-6,500 ft. Location: Worldwide, but especially common around coasts and mountains Precipitation: No more than light drizzle Composition: Liquid water Formation: Advective or radiative cooling

Stratocumulus Clouds ( The low, puffy layers ) Similar to cumulus clouds in form and composition, stratocumulus clouds are textured and puffy, but also joined into a semi-continuous layer Stratocumulus clouds usually form from cumulus or stratus clouds Typical Altitude: 2,000-6,500 ft. Location: Worldwide very common Precipitation: Occasional light rain, snow Composition: Liquid water Formation: Spreading and joining of cumulus clouds below a temperature inversion, wind turbulence in a stratus layer

Altocumulus Clouds ( Layers of bread rolls ) Since altocumulus clouds are high in the sky, they are generally above the influence of thermals, and form very differently from cumulus and stratocumulus clouds, who share similar names. Typical Altitude: 6,500-18,000 ft. Location: Worldwide Precipitation: Very occasional light rain Composition: Mostly liquid water, may also contain ice crystals Formation: Mid-level atmospheric disturbances and wave propagation (from e.g. mountatins)

Altostratus Clouds ( The boring clouds ) Below 6,500 ft. it s stratus Between 6,500 and 23,000 ft. it s altostratus Boring! but being so high up, they do make for nice sunsets. Typical Altitude: 6,500-16,500 ft. Location: Worldwide, common in middle latitudes Precipitation: Occasional light rain, snow Composition: Both liquid water, and ice crystals Formation: Usually formed from the thickening and lowering of a cirrostratus cloud on its way to becoming a nimbostratus cloud Altostratus Altocumulus Altostratus are potentially dangerous to aircraft because they can cause ice accumulation on the wings.

Nimbostratus Clouds ( Rainy day clouds ) The nimbostratus cloud has no species or varieties. It is a thick, wet blanket with a ragged base caused by the continual precipitation Typical Altitude: 2,000-18,000 ft. Location: Worldwide, common in middle latitudes Precipitation: Moderate to heavy rain or snow, which is generally steady and prolonged Composition: Liquid water, raindrops snowflakes and ice crystals Formation: Usually formed from the thickening and lowering of a altostratus cloud

Cirrus Clouds ( Delicate cloud streaks ) Cirrus clouds are the highest of all clouds and are composed entirely of ice crystals. Cirrus clouds are precipitating clouds, although the ice crystals evaporate high above the earth s surface. Typical Altitude: 16,500-45,000 ft. Location: Worldwide Precipitation: None that reaches ground Composition: Ice crystals Formation: Fall streaks of ice crystals in upper troposphere winds The crystals, caught in 100-150 mph winds create wisps of cloud.

Cirrocumulus Clouds ( Regularly spaced cloudlets, often rippled ) Cirrocumulus clouds are usually a transitional phase between cirrus and cirrostratus clouds. Large numbers of cirrocumulus clouds may indicate poor weather is approaching. Typical Altitude: 16,500-45,000 ft. Location: Worldwide Precipitation: None that reaches ground Composition: Ice crystals Formation: Cloudlets formed by choppy winds and high moisture levels in upper troposphere

Cirrostratus Clouds ( Delicate cloud streaks ) Cirrostratus clouds are difficult to spot and appear as a pale, milky lightening of the sky. Cirrostratus clouds never block out the sun completely, but rather produce a variety of optical effects. Typical Altitude: 20,000-42,000 ft. Location: Worldwide Precipitation: None Composition: Ice crystals Formation: Spreading and joining of cirrus clouds

Contrails and Others cirrostratus cirrus contrails cirrus Cumulus Kelvin-Helmholtz Wave Clouds